1. Field of the Invention
The present invention relates to an insole heater element and/or to an insole incorporating such an element for footwear. For example, the invention relates to a breathable porous flexible insole heater and optionally to an associated functional chemical delivery system for footwear.
2. Related Art
The design and utilisation of heater systems for footwear, particularly for ski-boot applications are known. See, for example, U.S. Pat. Nos. 5,041,717 and 4,798,933. These documents teach the use of a rigid electrical heating element embedded or otherwise fixed into a removable shoe insole unit, which can be cut to size as desired. An electrical connection to a battery is also provided, designed to be carried by the user.
Known heater elements for such applications are limited by: their comparatively high manufacturing complexity and hence cost; their thickness and rigidity; their lack of breathability to accommodate the microclimate conditions of footwear; the restricted area over which heating is applied and their limited design potential (in terms of aesthetics and capacity to be personalised). A further limitation of known insole heaters is the cumbersome design of the electrical connection, which can sometimes be felt by the wearer as it passes beneath the main body of the insole when in use. This is at least one reason why known heater insoles have high thickness.